Exemplary embodiments relate generally to memory devices, and more particularly to providing an upgradeable hard disk (UHD).
Redundant Array of Independent Disks (RAID) is a technology that employs the simultaneous use of two or more hard disk drives to achieve greater levels of performance, reliability, and/or larger data volume sizes. RAID has become a term that is utilized to describe computer data storage schemes that can divide and replicate data among multiple hard disk drives. RAID's various designs all involve two key design goals: increased data reliability and increased input/output performance. When several physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across several disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes. A RAID configuration affects reliability and performance in different ways. The problem with using more disks is that it is more likely that one will go wrong, but by using error checking the total system can be made more reliable by being able to survive and repair the failure. Basic mirroring can speed up reading data as a system can read different data from both the disks, but it may be slow for writing if the configuration requires that both disks must confirm that the data is correctly written. Striping is often used for performance, where it allows sequences of data to be read from multiple disks at the same time. Error checking typically will slow the system down as data needs to be read from several places and compared. The design of RAID systems is therefore a compromise and understanding the requirements of a system is important.
Secure digital (SD) cards are commodity storage products. They typically have relatively slow write and fast read capabilities and onboard circuitry that spreads the load evenly across all cells to prevent premature failure (e.g., logical to physical mapping). An SD card has a finite life span that can range from one hundred thousand to one million to ten million writes to a storage cell before failure. SD cards may be logically fragmented, but physically each cell has the same access time. Individual SD cards have individual performance characteristics with current speeds ranging up to about twenty-two megabytes per second (MB/S). Currently, there are two standards for SD cards, SD cards which may store from eight megabytes (MBs) to four gigabytes (GBs) per card, and SD high capacity (SDHC) which may store from four GBs to two terabytes (TBs) per card. Further, SD cards currently have three form factors: SD, mini SD, and micro SD, which are all electronically compatible with a passive adapter to make them interchangeable.